This prospective double-blind, placebo-controlled, multicenter trial will determine the effect of oral vitamin A (400 I.U.) and calcium supplementation (1000 mg Ca carbonate/day) given for two years on bone mineral density in JRA patients. Patients will participate in the double- blind portion of the trial for two years, then followup for approximately two years more. During this four-year period, each subject will be evaluated every six months.